Pneumatic circulation drier



y 2, 1939- E. SCHNEIDER 2,156,924

PNEUMATIC CIRCULATION DRIER Filed Dec. 51, 1935 s Sheets-Sheet 1 FE'EGEE FURNA ca M y 2, 1939. E. SCHNEIIDER 2,156,924

PNEUMATIC C IRCULATION DRIER Filed Dec. 51, 1935 s Sheets-Sheet 2 DEFL EC rm all y 1939- E. SCHNEIDER 2,156,924

PNEUMATI C C IRGULATION DRIER Filed Dec 51,1935 5 Sheets-Sheet 3 wlecrag CAP [em/.57 SCHNE/QEQ.

Patented May 2, 1939 I PNEUMATIC CIRCULATION DRIER Ernst Schneider, Uerdingen-on-the-Rhine, Gery, gesellschaft, many assignor to Buttner-Wcrke Aktien- Uerdingen, (Niederrhein) Ger- Application December 31, 15235, Serial No. 56,907

In Germany January 2, 1935 I 7 Claims.

Application for patent has been filed in Germany No. 3168,15? V/82a, on January 2, 1935.

There is a well-known type of pneumatic drying plant, in which the drying of the material is effected by means of a hot gas current between the feeder for the wet material and the separator where the dried material is separated from the gas current. In thisjtype of drier, the whole of the wet material travels along a drying path oi uniform length. The driers in question have the disadvantage that the water content of the dried material varies considerably. This is due to the fluctuations which are unavoidable with drying plants, fluctuations due to differences in regard to the grading and the moisture content of the material to be dealt with, and to differences due to the constant variations of the temperature and the volume of the drying gases and finally, to the fact that the feed can never be absolutely uniform at all times. Only the so-called circulation drier which was developed at a later date fulfils the said requirement viz. to deliver a uniformly dried material. This is" due to the fact that at the end of the drying path a separator is arranged by which the particles which are sufficiently dried are separated from the particles which are not sufficiently dried, the latter particles being allowed to pass into a splitting or crushing device where they are reduced to a grading which is more favourable for thedrying process, and subsequently returned into the drying path at the beginning.

However, a circulation drier of the type known hitherto, via, a type which combines the operations of drying, classifying and breaking would not suit the cases where the material to be dried, v for instance, slack coal as used for briquetting' purposes, which previous to being dried, has already the grading required for the subsequent process and, therefore, must not be reduced any further.

The object of the present invention is to provide a pneumatic circulation drier which is par-- ticularly suitable for all drying problems where it is essential that the breakage of the material, and therefore the production of fines during. an energetic drying operation, are reduced to a minimumand that also the heavy fluctuations in regard to the water content of the finished products, fluctuations .unavoidable with pneumatic driers which have no circulation, are kept as low as possible.

The salient feature of this type of drier as compared with the existing types is that at the end of the drying path the material is separated from the gas current as completely as possible without being classified, and that the greater portion of the material is subsequently re-fed into the drying path, whereas a small portion is discharged as finished material in regulated quantities, with its gradings remaining unchanged. As already mentioned .above, there is a wellknown type of pneumatic drier without circulation, in which the material also passes through the drier without intermediate classifying. However, the circulation drier which is the object of this invention represents in regard to these pneumatic driers which have no circulation, a very material improvement, in particular in such cases where for certain reasons a preliminary crushing of the material is avoided. This will exposes a larger area of moist surfaces as in the case of the circulation drier which is the object of this invention. It follows furtherthat in 'a pneumatic-drier without circulation the drying of the finer gradings is quicker than the drying of the coarser gradings, and this is the reason for the larger differences in regard to the water content of the finished material.

,The circulation drier according to this invention further enables the average fluctuations in regard to the water content of the finished material to be reduced to an extent which is greater, the more the circulation is accelerated.

. 4 Three embodiments of the invention are illustrated diagrammatically in the accompanyingdrawings.

Referring to Fig. l of the drawings, the hot gases produced in a furnace a are drawn by means of afan I; through a vertical pipe 0. The a feeder d delivers the wet' material into the said gas current which travels upwardly and after passing through a deflector cap e which changes the direction of flow of the, gases and material being treated from an upward to a downward direction carries the material into a screw conveyer i. In order to' avoid undue wear due to the impact of the material against the; walls of the deflector cap, the dimensions of the deflector cap are as large as possible. From the screw conveyer f, the larger portion of the material is forthwith discharged by an adjustable device g, whereas a regulated smaller portion descends through a chute it into the hot gas current denoted by the reference letter 9 which was taken off in a lateral direction from the pipe c at a point i and, as far as possible, liberated from the material in the process, the hot gas currentj forwarding thematerial in a well known manner into a separator k. The material discharged from the screw conveyor 1 by the adjustable device g is re-fed into the vertical pipe by means of the return pipe 1 and subsequently has to travel through the drier again.

In the plant shown in Fig. 2 a coarse classifier m is arranged above a return pipe I and the hot gas current a which was branched off and separated at point i as in Figure l, is allowed to pass through the upper part of the said classifier, so that by this gas current the fine particles contalned in the material delivered by the adjustable device a are entrained as finished material whereas the coarse particles are separated out and re-fed to the drier, by means of the return pipe Z.

The drier shown in Fig. 3 is based upon the same idea of eliminating the finest particles, the difference being that the elimination of the finest particles is performed mechanically by means of a screen sifter denoted by the reference letter 0.

It should be mentioned that it is quite feasible that the principle of returning an adjustable proportion of the material of various gradings, where a classifying is avoided, may also be ap plied to mechanical driers or other types, such as rotary drum driers, tube driers, etc., driers in which also an energetic drying action takes place. Moreover, there is the possibility of arranging a preliminary drying path in the usual manner in front of the pneumatic drier proper.

I claim:

1. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a pipe line connecting said material classifier with said hot air or gas generator, means for effecting a circulation of hot air or gases through said pipe line, means for introducing material to be dried into said pipe line, means-intermediate of the ends of said pipe line for extracting a portion of the material from the bulk of material in the pipe line, means for presenting a portion of said material extracted to the material classifier, and means for returning the remainder of the material to the pipe line.

2. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a pipe line connecting said material classifier with said hot air or gas generator, means for effecting a circulation of hot air or gases through said pipe line, means for introducing material of different grades or sizes to be dried into said pipe line, means intermediate of the ends of said pipe line for extracting a portion of the material from the bulk of the material in the pipe line, said extracted portion being comprised of different grades or sizes, meansfor presenting a portion of said material extracted to the material classifier, and means for returning the remainder of the material to the pipe line.

3. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a conveyor interposed with respect to said hot air or gas generator and said material classifier, a pipe line connecting said material classifier with said hot air or gas generator, said pipe line having a vertical flight terminating at one end of said conveyor, means for effecting a circulation of hot air or gases through said pipe line, means for introducing a material to be dried into said pipe line through a portion of which it is transmitted to said conveyor wherein a portion of said material is separated from the bulk of material delivered thereto, means for delivering that portion of the material extracted from the bulk to the material classifier, and means for returning the remainder of the bulk of material to the pipe line.

4. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a conveyor interposed with respect to said hot air or gas generator and said material classifier, a pipe line connecting said conveyor with said hot air or gas generator, a branch pipe leading from said pipe line at a point in advance of said conveyor, to the material classifier, means for effecting a circulation of hot air or gases through said pipe line, the branch thereof and said material classifier, means for introducing a material to be dried into said pipe line by which it is introduced to the conveyor wherein a portion of the material is separated from the bulk of material delivered thereto, means connecting the conveyor with the aforementioned branch pipe to deliver the separated material to the material classifier, and means for returning the remaining bulk of the material to the aforementioned pipe line.

5. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a conveyor interposed with respect to said hot air or gas generator and said material classifier, a pipe line connecting said conveyor with said hot air or gas generator, a branch pipe leading from" said pipe line'at a point in advance of said conveyor, to the material classifier, means for effecting a circulation of hot air or gases through said pipe line, the branch thereof and said material classifier, means for introducing a material to be dried into said pipe line by which it is introduced to the conveyor wherein a portion of the material is separated from the bulk of 'material delivered thereto, means connecting the conveyor with the aforementioned branch pipe to deliver the separated material to the branch pipe, and means for returning the remaining bulk'of the material to the aforementioned pipe line, said last mentioned means including a classifier for receiving the material from said conveyor.

6. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material branch pipe, a conveyor interposed with respect to said hot air or gas generator and said material branch pipe, apipe line connecting said conveyor with said hot air or gas generator, a branch-pipe leading from said pipe line at a point in advance of said conveyor, to the material branch pipe, means for effecting a circulation of hot air or gases through said pipe line, the branch thereof and said material branch pipe, means for introducing a material to be dried into said pipe line by which it is introduced to the conveyor wherein a portion of the material is separated from the bulk of material delivered thereto, means connecting the conveyor with the aforementioned branch pipe to deliver the separated material to the branch pipe, and means for returning the remaining bulk of the material to the aforementioned pipe line, said last mentioned means including a classifier interposed in the branch line leading from the main pipe line and having communication therewith.

'7. A drying apparatus of the pneumatic type comprising in combination, a hot air or gas generator, a material classifier, a conveyor interposed with respect to said hot air or gas generator and said material classifier, a pipe line connecting said conveyor with said hot air or gas generator, a branch-pipe leading from said pipe line at a point in advance of said conveyor, to the material classifier, means for effecting a circulation of hot air or gases through said pipe line, the

branch thereof and said material classifier, means for introducing a material to be dried into said pipe line by which it is introduced to the conveyor wherein a portion of the material is separated from the bulk of material delivered thereto,

means connecting the conveyor with the aforementioned branch pipe to deliver the separated material to the branch pipe, and means for returning the remaining bulk of the material to the aforementioned pipeline, said last mentioned means including a classifier interposed in the brancn line of the pipe line at a point between its connection with the main pipe line and the conveyer, whereby the finer particles of the returning bulk will be separated therefrom and presented with the material separated by the conveyor to the material grader.

ERNST' SCHNEIDER. 

